In the case of such powder-spraying devices there is, on the one hand, a need for decreasing as far as possible the amount of work necessary on changing the powder so that a changeover to another sort of powder may take place as quickly as possible, while, on the other hand, the device is to take up as little space as possible; this, however, frequently impedes cleaning and powder change.
For example, in the powder-spraying device described in French patent 2,369,878 there is a powder carriage which may be moved out of its position under the spray booth and which is joined by way of a fastener with a stationary aspiration pipe and two compressed-air pipes. Furthermore, the powder carriage has a connection for a spray gun, which is to be energized by way of a separate high-voltage cable. With such a system it is possible to speed up the powder change because only the powder carriage needs to be moved out of its position so that the booth may be cleaned and a new powder carriage can be put in. However, a filter unit is placed between the spray chamber of the booth and its sloping floor while the powder box is placed at a higher level whereby the powder must first be circulated by way of a special transport system before it is able to be strained or sifted and run into the powder box. These details of design make the device unnecessarily complex; trouble conditions are likely and furthermore, for many purposes, the booth is not low enough.